a pad trial judged under two different lamps

Our UR5e gripper trial left a faint band on finished collars. I can see it at the inspection bench; the supplier's return photos look spotless. Different lighting and angles, so we're arguing about pictures rather than parts. What should a shared appearance check specify before we compare pad materials? Holding and clean release still need testing too. A lovely collar stuck to a soft pad isn't much of a result.